1. Field of the Invention
The present invention relates to liquid crystal compositions useful in a variety of applications, including materials of various types of optical members such as optically anisotropic films and heat shield films. The invention also relates to compounds for use in such liquid crystal compositions, and to polymer materials and films that use such compositions and compounds.
2. Background Art
In an optically anisotropic film formed by aligning liquid crystal molecules on a transparent support and fixing the alignment state, the liquid crystal molecules are aligned by an alignment process on the support. However, it is extremely difficult to uniformly align (i.e. in monodomain alignment) the liquid crystal molecules all the way from the support to the air interface solely by the alignment regulation exerted by the support. This is because of the disturbed liquid crystal alignment due to the lack of alignment regulation on the side of the interface not subjected to the alignment process (air interface). The non-uniform alignment of liquid crystal molecules causes scattering of light due to disclination, and a nontransparent film is formed. Such a film is not desirable from the standpoint of improving its viewability, and a technique is needed that improves the alignment disturbance on the air interface side.
Out of these needs, techniques have been developed that uniformly align liquid crystal molecules by an alignment regulation provided also on the air interface side of the liquid crystal film not subjected to an alignment process, using a liquid crystal composition that contains a compound of primarily a discotic core and a long-chain fluorinated alkyl group, without using an alignment film on the side not subjected to an alignment process (for example, Patent Reference 1).
However, a problem occurs when such a liquid crystal composition containing a compound of primarily a discotic core and a long-chain fluorinated alkyl group is used to form an optically anisotropic film as a support, and another optically anisotropic film is laminated on this support to produce an optically anisotropic film laminate. Specifically, the first layer has a low surface energy, and cissing occurs when these films are laminated. As a countermeasure against this problem, Patent Reference 2 describes forming a cissing-free, uniform coating with the use of a compound containing a the discotic core and a long-chain fluorinated alkyl group wherein the core is substituted with an acidic group or a derivative thereof.
Patent Reference 3 describes an ionic thermotropic columnar fluorine-containing liquid crystal compound similar in structure to the compound described in Patent Reference 2. However, this publication does not investigate the liquid crystal orientation of the film formed by using the compound, and the cissing that might occur when laminating the film.